Timing of Renal Replacement Therapy in Acute Kidney Injury: Shedding New Light on an Old Controversy

Critically ill patients with severe acute kidney injury (AKI-D) require renal replacement therapy (RRT) increasingly. However, the optimal timing of initiation of RRT for non-life-threatening indications of AKI remains unknown. There is a debate as to whether different philosophies of RRT initiation (early vs. delayed) confer a survival benefit. Lowering the threshold for RRT initiation, however, inevitably leads to more critically ill patients receiving unnecessary RRT. The relevant proportion of nonprogressing early stage AKI patients with spontaneous kidney recovery is a matter of severe concern because RRT has potentially lethal complications and is expensive. Moreover, these patients should be excluded from randomized trials. The furosemide stress test in critically ill patients with early stages of AKI serves as a novel tubular function test to identify those patients with severe and progressive AKI-D. Future trials to validate findings of a promising pilot study are warranted.